The present invention relates to an arrangement for treating sheet-material webs by corona discharge. In particular, it relates to such an arrangement wherein the webs are treated by corona discharge and which is provided with a control for controlling the position of the edges of the web.
In many sheet-material treating applications, for example in extruders for synthetic plastic foils, in printing machines, in coating machines or the like, it is highly important that the position of one or both edges of an advancing web or foil be precisely controlled. For this purpose it is known to provide so-called edge position controls.
Machines of this general type also frequently utilize devices for producing corona discharges. The purpose is to treat one or both surfaces of the web by means of the discharges with the result that the bonding capability of the treated surfaces, for example bonding to a coating layer or the like, is improved thereby. Such a corona discharge device is described in British Pat. No. 925,354.
Both of these types of equipment require space for installation. Space is, however, often at a premium in this type of equipment and this is a disadvantage. Furthermore, the edge control device changes the position of the edges and hence of the entire web either before or after passage of the web through the corona discharge device, since the web must be repositioned prior to advance to a further processing station, for example a printing station, such adjustments involve complementary adjustments to the electrodes which produce the corona discharge. This is also a disadvantage of the prior art.